Materials testing grip



- R. c. CAVANAUGH "MATERIALS 'rsswrue GRIP Sept. 26,1 967 Filed May 25, 1965 United States Patent 3,343,407 MATERIALS TESTING GRIP Ronald C. Cavanaugh, Holbrook, Mass., assignor to Instron Corporation, Canton, Mass., a corporation of Massachusetts Filed May 26, 1965, Ser. No. 458,865 8 Claims. (Cl. 73-103) ABSTRACT OF THE DISCLOSURE A gripping device for use in testing the strength of belt-like materials having concentrically arranged inner and outer capstans. The inner capstan consists of split portions for gripping the specimen which is wound around the inner capstan and the outer capstan. The inner capstan is rotatable with respect to the outer capstan and is locked after the specimen is secured.

This invention relates to grip apparatus for testing high strength belt and tape material, such as seat belts, and more particularly to an improved grip for use in such apparatus.

Objects of the invention are to provide a testing grip for belt-like specimens having improved loading characteristics and eflicient gripping action to produce proper breaks within the gage length of the specimen, while preserving structural simplicity and reliability. The invention features a double capstan arrangement in which the specimen is loaded into the separately rotatable inner capstan and wound around specimen receiving surfaces of both the inner and outer capstans before leaving the grip.

Other objects, features, and advantages will appear from the following description of a preferred embodiment of the invention, taken together with the attached drawings thereof, in which:

' FIG. 1 is an elevation of a testing grip according to the invention, with internal parts shown in broken lines;

FIG. 2 is a section through 2-2 of FIG. .1;

FIG. 3 is a section through 33 of FIG. 2;

FIG. 4 is a section through 44 of FIG. 1; and FIG. 5 is a schematic diagram showing a specimen loaded in a pair of grips.

Referring now more particularly to thedrawings, there is shown in FIG. 1 a testing grip having a frame 12 with a pair of spaced side portions 14, 16, between which is bolted an upwardly extending shank portion 18 for insertion into associated testing apparatus (not shown).

Frame 12 is cast integrally with outer capstan 20, said outer capstan providing a generally cylindrical specimen receiving surface 22, a portion of which is disposed between frame side portions 14, 16, and the rest of which is depressed slghtly from the lateral margins 23, 24 of capstan 20. An opening 26 extends radially through capstan 20, across the full width of surface 22 between frame portions 14, 16. The resulting free ends 28, 30 are rounded off, with surface 22 tapering inwardly somewhat adjacent end 30. An axial bore 32 extends entirely through the frame and outer capstan, concentrically within surface 22.

A pair of similar generally disk shaped side flanges 36, 38 are rotatably mounted in frame 12 at the opposite ends of bore 32. Describing flange 38 as typical, it has an outermost portion 40 of diameter greater than that of bore 32, a bearing portion 42 that fits slidingly into bore 32, and an inner recess 44 of diameter smaller than that of bore 32.

Split inner capstan 48 comprises a fixed portion 50 and.

an adjustable portion 52, each of substantially semicircular cross section and together providing generally cylindrical specimen receiving surface 54. Both inner capstan portions extend between flanges 36 and 38, and are sup ported thereby in recesses 44, 44a. As seen in FIG. 2, fixed portion 50 is located at the bottom of the recesses and is fixed to the flanges 36 and 38 by camshaft 55, extending entirely through the flanges and inner capstan, and additionally by bolts'56, 58 (FIG. 1) passing through flange 38 into portion 50. Corresponding bolts (not shown) pass through flange 36. Cams 60, 62 are rotatably mounted on the opposite ends of shaft 55, respectively outside and adjacent flanges 36, 38. Each cam has a fingertip control lever, as at 64 in FIG. 1.

Adjustable portion 52 of inner capstan 48 is mounted at the top (FIG. 2) of recesses 44, 44a. Bolts 66, 68 extend respectively through slots 70, 72 in flanges 36, 38, into opposite ends of portion 52. Slots 70, 72 are wider than the diameter of bolts 66, 68, so that the bolts can be vertically adjusted to control the proximity of capstan portion 52 to portion 50. While portion 52 is free to slide vertically in flange recesses 44, 44a, it is restrained from rotation relative to the flanges by dowel 74 located in vertical slots in flange 38 and portion 52.

Bolts 66, 68 are biased toward the bottom of slots 70, 72 by spring assemblies 76, 76a respectively located in vertical bores 78, 78a in flanges 38 and 36, above said bolts. These assemblies comprise Teflon sliders 80, 800, which contact the bolts, coil springs 82, 82a, above the sliders, and adjustable set screws 84, 84a above the springs. Camming surfaces 61, 63 of cams 60, 62 contact the respective bolts from below, and thereby the position of adjustable capstan portion 52 can be controlled by rotating the cams. Sighting opening 86 (FIG. 1) in flange 36 allows visual observation of the inner capstan portions.

It will be appreciated that relative rotation of the inner and outer capstans is obtained by rotating the total assembly of flanges 36, 38 and the inner capstan in bore 32. To control this rotation, a detent pin 90 passes through axial bore 92 (FIG. 4) in outer capstan 20. The ends of pin 90 extend beyond capstan 20 and through vertical slots 94, 96 in outermost portions 40a, 40 of flanges 36, 38. Slot 98 is located in pin 90 near its left end, and the right end of the pin is correspondingly cut away to pro- 'duce slot or recess 100. Pin 90 is stepped down to the left of shoulder 102 and bore 92 is stepped up to the right of shoulder 104, providing a space for coil spring 106 surrounding the pin between said shoulders. Spring 106 acts to bias pin 90 to the right, with slots 98, out of alignment with flange portions 40a, 40. With the pin in its rightward or locked position relative capstan rotation is prevented.

At the right hand end of pin 90 elbow 108 is bolted to the outside of flange 38. Shaft 110 is slidingly disposed in horizontal bore 112 in elbow 108, aligned with pin 90. Cap portion 114, of a diameter larger than that of bore 112 is mounted on the left end of shaft 110, and knob 116 screws on to the right end of said shaft.

Set screw 118 incapstan 20 extends into horizontal slot 120 in pin 90, in order to align the pin with slots 98, 100 opening downwardly. I

The inner capstan portions 50, 52 are oriented so that the opening between their opposing serrated faces 51, 53 is adjacent opening 26 through outer capstan 20 when the ends of pin 90 are engaged in slots 94, 96.

In operation, with the inner capstan in the initial circumferential position shown in FIGS. 1-4, cams 60, 62 are rotated to the position shown in FIG. 1, raising bolts 66, 68 in slots 70, 72 and inner capstan portion 52 away is pushed to the left, cap 114 forcing pin 90 leftwardly against spring 92, until the pin reaches its unlocked position when slots 98, 100 are respectively aligned with outermost flange portions 40a, 40 at slots 94, 96. Knob 116 is now moved in a circular path, which causes flanges 36, 38, as well as the inner capstan, to rotate in bore 32 about an axis parallel to specimen receiving surfaces 22 and 54. During this rotation, flange portions 40a, 40 ride in slots 98, 100, holding pin 90 in its unlocked position even though shaft 110 is out of alignment with the pin.

When a rotation of 360 has been completed pin 90 will be realigned with slots 94, 96 and shaft 110, and the specimen will 'be wound around the entirety of receiving surface 54 of the inner capstan. Knob 116 is released, returning pin 90 to its locked position to prevent further capstan rotation. The free end of the specimen is now wound around surface 22 of the outer capstan, and subsequently loaded into the second grip. The resulting arrangement is shown schematically in FIG. 5.

Other embodiments will occur to those skilled in the art and are within the following claims.

What is claimed is:

1. A grip for use in testing a specimen, comprising a frame;

a first capstan supported by said frame and having a first specimen receiving surface;

a second capstan having a second specimen receiving surface and mounted for rotation relative to said first capstan about an axis parallel to both of said receiving surfaces;

one of said capstans having a securing portion for securing an end of said specimen and being mounted inside the other capstan;

said other capstan having an opening through its specimen receiving surface communicating with the specimen receiving surface of said one capstan, said opening being sized to admit said specimen; and

a locking member having a locked position in which relative rotation of said capstans is prevented and an unlocked position in which said rotation is permitted.

2. The grip of claim 1 further comprising a flange portion adjacent said locking member, said locking member having a slot, said capstans having an initial position of relative rotation in which said locking member is free to move between its locked and unlocked positions, said flange portion interlocking with said slot whenever said capstans are not in said initial position of relative rotation, said flange portion holding said locking member in its unlocked position when interlocked with said slot.

3. The grip of claim 2 wherein said opening in said other capstan is so located to be adjacent said securing portion of said one capstan when said capstans are in said initial position.

4. The grip of claim 3 wherein said locking member comprises a detent pin disposed in said other capstan and said flange portion is rotationally fixed to said one capstan, said flange portion having a slot aligned with said pin when said capstans are in said initial position, said pin being slidable in said other capstan when said capstans are in said initial position between its unlocked position in which said slot in said pin is aligned with said flange portion and its locked position in which said slot in said pin is out of alignment with said flange portion.

5. The grip of claim 1 wherein said one capstan comprises a pair of separate portions each of generally semicircular cross section, one of said portions being adjustable toward and away from the other of said portions, the non-cylindrical surfaces of said portions opposing each other to form said securing portion.

6. The grip of claim 5 further comprising a member extending laterally out from said adjustable portion of said one capstan, and a cam disposed adjacent said extending member, said cam being fixed translationally relative to said other portion of said one capstan but free to rotate relative to said other portion, the rotational position of said cam thereby controlling the proximity of said adjustable portion to said other portion of said one capstan.

7. The grip of claim 5 further comprising a spring assembly for biasing said adjustable portion of said one capstan against said other portion of said one capstan.

8. A grip for use in testing a belt-like specimen, comprising a frame,

a shank portion extending from said apparatus for installing said grip in associated testing appratus,

a first capstan supported by said frame and having a generally cylindrical first specimen receiving surface with an opening therethrough sized to admit said specimen, and an axial bore extending entirely through said first capstan,

a pair of flanges rotatably mounted in said first capstan at opposite ends of said axial bore,

a sec-0nd capstan having a second generally cylindrical specimen receiving surface mounted in said axial bore between said flanges, said second capstan comprising a pair of separate portions each of generally semicircular cross section, one of said portions being fixed to said flanges, the other of said portions being adjustable toward and away from said fixed portion, the non-cylindrical surfaces of said portions being serrated and opposing each other,

a pair of members extending laterally out from opposite ends of said adjustable portion of said second capsta n,

a pair of cams rotatably mounted on said flanges respectively adjacent said extending members, the rotational positions of said cams thereby controlling the proximity of said adjustable portion to said fixed portion of said second capstan,

a locking member having a locked position in which relative rotation of said capstan is prevented and an unlocked position in which said rotation is permitted, said locking member comprising a detent pin slidably mounted in said first capstan and extending beyond the ends of said first capstan into a pair of slots in said flanges, said pin having a pair of slots: located to register with said flanges when said pin is: in its unlocked position and to be out of registry with said flanges when said pin is in its locked position,

a spring biasing said detent pin in its unlocked position,

and a shaft with a knob theereon secured to one of said flanges in position to register with said detent pin when said pin is in its locked position, said shaft being axially slidable relative to said flange when said pin is in its locked position to control the position of said pin.

References Cited UNITED STATES PATENTS 529,648 11/1894 Green 254-161 286,680 6/1963 Gloor 73-103 3,196,671 7/1965 Dannis 7395 FOREIGN PATENTS 8 6,048 1l/ 1917 Switzerland. 717,731 9/ 1965 Canada.

JAMES J. GILL, Primary Examiner.

RICHARD C. QUEISSER, Examiner.

J. D. SCHNEIDER, Assistant Examiner. 

1. A GRIP FOR USE IN TESTING A SPECIMEN, COMPRISING A FRAME; A FIRST CAPSTAN SUPPORTED BY SAID FRAME AND HAVING A FIRST SPECIMEN RECEIVING SURFACE; A SECOND CAPSTAN HAVING A SECOND SPECIMEN RECEIVING SURFACE AND MOUNTED FOR ROTATION RELATIVE TO SAID FIRST CAPSTAN ABOUT AN AXIS PARALLEL TO BOTH OF SAID RECEIVING SURFACE; ONE OF SAID CAPSTANS HAVING A SECURING PORTION FOR SECURING AN END OF SAID SPECIMEN AND BEING MOUNTED INSIDE THE OTHER CAPSTAN; SAID OTHER CAPSTAN HAVING AN OPENING THROUGH ITS SPECIMEN RECEIVING SURFACE COMMUNICATING WITH THE SPECIMEN RECEIVING SURFACE OF SAID ONE CAPSTAN, SAID OPENING BEING SIZED TO ADMIT SAID SPECIMEN; AND A LOCKING MEMBER HAVING A LOCKED POSITION IN WHICH RELATIVE ROTATION OF SAID CAPSTANS IS PREVENTED AND AN UNLOCKED POSITION IN WHICH SAID ROTATION IS PERMITTED. 